128 THE SALTON SEA. 



The strand of 1907 on Obsidian Island bore a heavy growth of Pluchea sericea on East 

 Bay in November 1908, with which were growing a few Heliotropium, Sesuvium, Distichlis, 

 and Cucurbita. The exposed gravelly and sandy strip on the southeastern part of the island 

 showed some Lippia nudiflora, Pluchea sericea, one Eclipta alba, Aster spinosus, and a 

 particularly robust form of A. exilis. Baccharis glutinosa and Eriogonum thomasii were 

 still present. One Prosopis was seen on East Bay, one on the southeastern point, and one 

 on West Bay as earlier, and all had made a notable growth. Parosela was established on 

 the shore back from West Bay, but Oligomeris, Sonchus, Bumex, Cryptanthe, Psathyrotes, 

 Leptochloa, and Atriplex were not found. Some of these had doubtless fruited and might 

 appear later as a continuation of the original introduction. (Plate 29 a.) 



The strand of 1907 at Travertine Terrace bore Sesuvium, Heliotropium, Pluchea cam- 

 phor ata, Atriplex polycarpa, and A. canescens, although the rank of seedlings at the foot 

 of the cut bank had perished. Distichlis, Spirostachys, Suceda, Prosopis pubescens, Astragalus, 

 Juncus cooperi, Bouteloua arenosa, and Phragmites were also present. All of these except 

 Phragmites and Atriplex canescens had appeared since the examination in February. The 

 increase in the population was of a character widely different from that of the other areas in 

 which the grains had been balanced or overbalanced by the losses. The high cut bank at the 

 upper part of the area had continued to crumble and also showed marked effects of wind 

 erosion. The location was especially favorable to invasion by wind-borne seeds. (Plate 18 b.) 



The course of the voyage for circumnavigating the lake in November 1908 gave fav- 

 orable opportunities for examination of the strand of 1907 elsewhere, and a landing was 

 made on the sandy shore of the southwestern part of the lake, which was of such slope 

 as to show a recession of about 200 feet. Spirostachys, Coldenia, Pluchea sericea, Parosela 

 spinosa, Heliotropium, and Eriogonum were the principal members of the invading popula- 

 tion. The last-named species had undergone a remarkable endurance of untoward condi- 

 tions in one place. First a group of these plants, with woody stems less than a yard in 

 height, had been overtaken by a sand dune, with the result that the tips of the stems were 

 bent over until they touched the ground. Upright branches arose from the apices, but 

 now the making of the lake submerged these plants for a period of a few months in water 

 containing from 0.25 to 0.33 per cent of saline material. These plants were in bloom at 

 the time of our visit in November 1908. 



A second landing on the western shore to the northward of this locality led to the 

 discovery of a plantlet of Salix nigra and representatives of Hilaria rigida, Encelia fru- 

 tescens, Olneya tesota, and Isocoma veneta var. acradenia, in addition to the commoner species 

 named above on the strand of 1907. 



The beaches received but scant attention in 1909. The midsummer season was char- 

 acterized by precipitation much above the average and a distinct run-off occurred over a 

 large share of the basin. This exerted an influence in two ways. In one the salts were 

 washed from the surface layer, while in another seeds were carried down in drainage lines 

 cutting across the emersed zones. 



The first visit to the observational areas in 1909 was made during the closing week 

 of October. The strand of 1907 on the Imperial Junction beach showed only Suceda, 

 Pluchea sericea, Atriplex, and Spirostachys, and the first-named was showing the stress of 

 aridity distinctly, great numbers of dead plants being present. The washes cutting across 

 this zone, as well as those of 1908 and 1909, had received a large supply of rain-water which 

 had been held with great tenacity by the adobe soil. In such places Suceda, Sesuvium, 

 Spirostachys, Pluchea sericea, Cucurbita, Chenopodium, and Baccharis were growing well' 

 All of^the Typha originally noted in this locality had died, but a plant which had been 

 cast ashore this year in the filled wash had survived, making a reintroduction of this plant 



The invasions on the shores of Obsidian Island were now seen to occupy several soil 

 complexes. Thus, one group of plants, comprising Pluchea sericea, Prosopis pubescens P 



